1. Field of Use
This invention relates generally to apparatus for automatically cleaning liquid conveying systems and to an improved control valve assembly in such apparatus. The invention is especially well-adapted for use in fluid conveying systems such as are used in dairies to convey milk from a milking parlor to a storage area.
2. Description of the Prior Art
Prior art liquid conveying systems used in dairies to convey milk from a milking parlor to a storage area typically comprise a pipeline to which teat claw assemblies for milking cows are connectable and the pipeline is connectable to a milk storage tank. Milk is moved through the teat claw assemblies, through the pipeline and into the milk storage tank by a vacuum which is maintained in the pipeline by means of a vacuum pump acting through a vacuum releaser which allows milk accumulating in the pipeline to be supplied to a milk storage tank. U.S. Pat. No. 3,191,576 discloses such a prior art system. Such systems must be cleaned after each milking operation. The prior art discloses various types of cleaning apparatus which are usable with such liquid conveying systems to periodically and repeatedly introduce cleaning liquids (in the form of cleaning solutions comprising mixtures of water and detergent and in the form of plain rinse water) into a cleaning liquid tank and from thence into the milk conveying systems in accordance with programs or cycles determined by a programmable timer. U.S. Pat. Nos. 3,191,576; 3,119,399; 3,921,652 and 3,732,891 illustrate various types of such prior art cleaning apparatus. The prior art cleaning apparatus has become increasingly more complex, costly, and trouble-prone, especially as regards the valves and valve controls required to control the flow of the cleaning solutions between the cleaning liquid tank and the milk conveying system. Furthermore, some types of prior art cleaning apparatus operate in such a manner that they are extremely wasteful of hot water and the relatively expensive detergents used to clean the liquid conveying system. For example, in some apparatus a batch of cleaning solution comprising hot water and detergent is used once on the initial cleaning cycle and must then be discarded because it is so contaminated with residual milk that it cannot be recirculated effectively. Accordingly, it is desirable to provide an improved cleaning apparatus and valve assembly therefor which overcomes these and other problems.